and, thanks to the internet, we met a few. 16-year-old cristos lives in greece and has taken more than five different computer courses. >> i now know what i want to study at university and what i want to do in my life. >> reporter: 22-year-old from kazakhstan got a job with twitter after taking artificial intelligence. >> you can gain all the top knowledge from a top university. >> reporter: in northern virginia, 14-year-old sophia and her mother, laura, have completed a variety of classes. >> you can sit on your couch in your pjs and learn about any topic that interests you. >> reporter: do you have a sense of what grade you would give yourself? >> probably an a minus. i'm a little rusty. i don't know about you. >> i would give myself an a plus. >> reporter: back at the university of pennsylvania, poetry professor says opening his class has changed his whole feeling about teaching. >> i like it because i get to teach people all over the world. they're self selective. because they're not getting credit at the moment and it's free, they come because they're interested in my topic, which